hi, I have an 02 mini r53. The idle will go from about 900rpm and then gradually increase to 2000rpm and then drop down quickly. It does this repeatedly, however it doesn't do this when the ac is on. I've been trying to fix the problem but can't seem to get it. I though replacing the spark plugs would cut it but that didn't work, and the battery is new. Please help

 

Check your coolant level and make sure there are no bubbles in the system. Do you also get any check engine light?

 

The coolant has been leaking, however whenever I top it off, the surging continues. I ran the codes and got p0507.

 

so i guess we need to stop that leak since it effects the coolant pressure in the system.

Also check this link i found https://www.northamericanmotoring.com/forums/stock-problems-issues/189439-p0171-and-p0507.html

Keep us posted